Effects of Bi addition on sintering and electrical properties of scandia stabilized zirocnia as intermediate-temperature SOFC electrolyte

The compatibility of bismuth compounds as a sintering aid for (ZrO ₂)_0.89(ScO_1.5)_0.1(CeO ₂)_0.01 (ScSZ) electrolyte in intermediate-temperature solid oxide fuel cells (IT-SOFCs) has been discussed. Addition of 3 mol% BiO₁₅ considerably decreased the sintering temperature of ScSZ of approximately 200 °C and achieved the densification with a relative density above 95% at 1200°C. The solid solubility limit of BiO_1.5 in ScSZ was less than 2 mol%. Dispersion of Bi₂O₃ at the grain boundaries correspondingly accelerated the growth of ScSZ grains and increased the grain boundary resistance at temperatures below 450 °C. At elevated temperatures of 450-750 °C, the electrical conductivity of the ScSZ after doping remained almost unchangeable in air and under reducing atmospheres. The results suggested that bismuth addition is promising to be applicable to a low-temperature co-firing fabrication of ScSZ based components for IT-SOFCs.